Thursday, April 19, 2007

Obesity: A Conjecture

Obesity is a current hot issue, problem, crisis ... . One reason is that it is a real problem. Another, I suspect, is that it provides people who want governments to do things with a new argument.

My evidence for that conjecture is how much of the talk about obesity focuses on the evils of marketers cleverly manipulating people into eating junk food. While sellers of junk food do, of course, advertise their products, so do sellers of diet soda, exercise equipment, metrecal and health foods. I understand why people concerned about obesity might see the regulation of advertising as a potentially useful tool--it is at least more likely to be politically viable than an attempt to ban hamburgers and french fries from the American diet. But I do not see marketing as a plausible explanation for the increasing frequency of obesity. It seems particularly implausible given that the increase is not limited to rich countries such as the U.S.; I doubt the consumption patterns of people in India or China are much influenced by advertising.

My alternative explanation for obesity is straightforward. Humans evolved in an environment where food was costly, fat scarce, sweetness a useful signal that fruit was ripe. We are designed by evolution to put on weight when we can as a precaution against future famines and to favor fat and sugar when we can get them. In a world where food is inexpensive and plentiful we are inclined to overeat, in particular to eat more fat and sugar than is good for us.

The obvious explanation of the increase in obesity is that real incomes around the world have been trending up for decades. Now poor people in the U.S., and increasingly in poorer parts of the world, can afford to eat all the calories they want. Since all the calories they want represents more than what they require, the result is that they get fat.

There is one problem with this explanation. According to the figures I have seen, in the U.S. obesity is less common in high income groups than in low income groups. The richer you are, the less your diet is constrained by cost, so we would expect higher income groups to be at least as obese as lower income groups. To explain why they are not I must add one additional factor: Time lags in adjusting behavior and social norms to changed circumstances.

Suppose you are part of a population where food has been costly, where people engage in a lot of physical labor, and so where the problem is getting enough to eat, not avoiding too much. You, and those around you, have adapted their behavior to that environment.

Now things change; food gets cheap, wages go up, almost everyone can afford to eat as much as he wants. For a while, perhaps a generation or two, people follow the old patterns in the new circumstances; the result is that many of them end up fat. Over time, although the hardwired elements of behavior do not change--evolution is slow--the cultural elements do. Instead of demonstrating how wealthy and generous you are by urging your guests to have a second and third helping of dinner, you do it by providing them smaller amounts of particularly tasty, sophisticated, or expensive dishes. Instead of making a point of avoiding physical exertion when you can, you enter the Boston Marathon. Eventually you and those around you have adapted your behavior, although not your hardwired tastes, to the new environment.

Well off people in developed societies have been able to afford second and third helpings at every meal for a long time. Hence, if my argument is right, they have had time to adapt to a world of plenty. For poor people, being able to eat all they want of more or less what they want is a newer thing, so they are still following the old ways--the pattern of the traditional Jewish (or Italian) mother who insists that her guests have a little more of this and that before they end their meal. Hence, if my conjecture is correct, greater obesity among the poor reflects the lag in adapting to circumstances that are relatively new for them. The rich have had time to adjust.

One implication of this is that, at some point in the past, richer people should have been more often obese than poorer--back when the rich were no longer constrained by the availability of food but the poor still were. That fits my casual impression, but I have no actual data to support it.

32 Comments:

Your explanation implies that obesity will become less of a problem in subsequent generations, which I am not confident about.

Another possible explanation for the high-income/low-income obesity split: Intelligence, which is correlated with income, has a significant genetic component. Tendency to obesity also has a genetic component. Some people will eat a lot, and not get fat, whereas others tend to get chubby even on relatively modest diets. I am not sure of exactly what the genetic component is, but I am fairly certain that there is some component. Some claim that the genetics is essentially all that matters regarding tendency to obesity. In our society, being thin is desirable. Thus, all else being equal, someone who is thin is more desirable as a mate than someone who is fat. Someone who is smart or rich is also more desirable as a mate. Thus, thin people will tend to mate with smart and rich people, more often that would be expected based on their other characteristics. Over several generations of such selective mating, the genes for intelligence and the genes for thinness will tend to be correlated to some degree. This requires that the ideal of thinness for beauty be at least several generations old in our society, and I think that's true.

Another thing: the halo effect. People tend to attribute to more beautiful (and thin) people positive attributes of other kinds, and thus thin people may be able to more easily achieve economic success, since their non-physical qualities are judged more favorably by others.

I agree with your analysis. However it is not only traditional Jewish and Italian mothers that try to fatten their children and grandchildren. It seems that my mother (French) and my wife's (Chinese) are in a constant competition to see which can make our children fatter, faster.

I think the hypothesis that obesity will become less of a problem is correct, though I'm not sure I completely agree about the mechanism that will bring this about.

Being healthy is not a public good -- an individual with a weight problem has a tremendous incentive to fix the problem, because being obese imposes substantial personal costs. (This is one reason why regulation is so clearly and obviously silly here -- there is no sign of "market failure" here.)

We can therefore expect that there will be significant market pressure to find ways to allow people to control their weight successfully. The diet book market sells a lot of units and has for decades, even though for most people diets are ineffective. Clearly there is a serious market here. Surgical interventions for the highly obese are rapidly spreading, which I think is further evidence for demand. The pharma companies are hot on the trail of the mechanisms behind appetite and are almost certain to come up with effective drugs to suppress it -- it seems clear to me that when they do, they will sell exceptionally well.

So, although I'm somewhat skeptical that those with high income tend to be thinner because they are "more used to" having more food than they need, I'm pretty much in agreement with the conclusion that over the medium term this problem is going to vanish on its own.

How much fat you accumulate depends strongly on the hormone cortisol which is generated under heavy stress. It helps you regain recources quickly after for example beeing chased by a tiger.The difference to normal fat accumulation is that with high cortisol level your fat is stored around the belly to be ready to use for important organs.

The better you are able to handle stress the less bellyfat you get. Childhood abuse is highly related to obesity.

adam: "In our society, being thin is desirable. Thus, all else being equal, someone who is thin is more desirable as a mate than someone who is fat."

Desirable is the right waist to hip ratio which depends on the position of the fat depots. If i.e. a girl becomes very thin at some point her hip bones will stick out which leads to a lower waist to hip ratio.

The pressure to be thin is imho more related to jealousy about food. It's a survival instinct.

jorge: "However it is not only traditional Jewish and Italian mothers that try to fatten their children and grandchildren."

Mothers are very proud of their "cooking skills" :) It's an insult to them to reject their food.

david: "...the U.S. obesity is less common in high income groups than in low income groups."

I think it has alot to do with the status hormone serotonin. The higher in the ranks you ascend the higher your serotonin level climbs.Low serotinin level makes people extremly stress sensitive and leads to high cortisol levels.

Evolution is not necessarily slow: Its speed is proportional to the amount of heritable phenotypic variation times the intensity of selection. It's slow when selection pressures are weak and heritabile variation is low, and fast when heritable variation is high and selection is strong. So if obesity carries a high fitness cost and has a large genetic component, we can expect adaptation to take care of the obesity problem in a few generations. If not, not.

Adam has already mentioned intelligence, which correlates not only with income but overall health. If intelligent people are better at consciously overriding their instinctive behavioral biases by thinking ahead (which seems to be the case), then this could also explain the variation we see.

Another possible explanation that needs serious consideration is infection. There's been a lot of findings recently linking obesity to pathogens (just google obesity germ). Generally any condition that imposes a significant fitness cost and exists for a long time (i.e. more than a few hundred years) at high rates in the population (i.e. more than 1 in 1000) is a good candidate for being caused by pathogens.

One implication of this is that, at some point in the past, richer people should have been more often obese than poorer--back when the rich were no longer constrained by the availability of food but the poor still were.

Henry VIII of England is one anecodtal data point.

adam: This requires that the ideal of thinness for beauty be at least several generations old in our society, and I think that's true.

What about all the ads in 1940s and 1950s US comic books selling products designed to rid girls of unwanted skinniness? That's suggestive that the ideal weight was significantly higher then than it is now.

I have an alternative explanation, which seems simpler, and is based on Seth Roberts' "Shangri-La Diet" principles.

Specifically, the body's set point is tied to the flavor-calorie association of foods. When you eat familiar flavors, there is a strong association, and the set point is increased b/c the body thinks it is a time of plenty. When you eat novel flavors, the set point goes down. Fast food, because it is made exactly the same way every time, has a strong flavor-calorie association.

So the alternative hypothesis is that low-income people tend to eat cheap, premade foods like fast food, which have a strong flavor-calorie association. People with middle and high incomes eat more food from restaraunts or other places, which have more variety in taste.

As evidence for this, or some other fast-food relationship, I believe the correlation between fast-food and obesity over time is substantial (both rising a lot in the last few decades). This is far from demonstrating causality, of course - some other aspect of fast foods may make them fattening, or a third factor may drive people to eat fast food. But it does seem relevant.

Patri's suggestion also has a lot going for it. Ultimately obesity is probably a condition that results in screwing the same intricate system up in any of a number of different ways (as seems likely to be the case with schizophrenia as well).

I agree with Patri. I have experience as someone who does not like to spend money, and sometimes struggles with fitness. It is very inexpensive to get your calorie requirement filled, but most of the foods which do this are either not terribly palatable, or loaded with addictive substances (high-glycemic carbs, trans-fats).

It is just not that easy to eat a healthy, non-addictive diet that tastes good without spending a fair amount of money on food. For the upper middle class and the rich, this is a non-issue. A fabulous array of food can be had on a typical such family's food budget. For someone with a median income raising a family (not even really poor) it's a different story. They have to choose diet health over things like entertainment or a nicer house, or not care much about taste.

matt: So if obesity carries a high fitness cost and has a large genetic component, we can expect adaptation to take care of the obesity problem in a few generations.

Our stomach is the main part in evolution. Bigger molecules eat smaller molecules. It's the same in every human beeing, in every animal. Humanity will end before people stay slim no matter what.Humans are basically moving stomaches.

matt: If intelligent people are better at consciously overriding their instinctive behavioral biases by thinking ahead..

The appetite is much stronger than your will. When your body needs something, it will get the right incredients to ensure that the metabolism is working properly. Your brain is built to get these incredients. Your best food advisor is in your head, it has worked for millions of years.

patri: So the alternative hypothesis is that low-income people tend to eat cheap, premade foods like fast food, which have a strong flavor-calorie association.

The main difference is that fast food contains lots of fat and sugar. This is precisely what the body needs in a stress situation. Therefore the term "fast". Getting a big energie package before the next tiger hunts you.

anonymous: one explanation for rich people not being obese in developed countries may simply have to do with their higher level of education, access to information and health conscience.

Put high educated people in a life crisis and they will all become fat. Many extremely intelligent people are very fat.

michael: For the upper middle class and the rich, this is a non-issue. A fabulous array of food can be had on a typical such family's food budget.

Rich people eat what their appetite tells them to eat. Many business people eat at fastfood restaurants all the time when on business tours.This is whining on a high level. Compared to poor contries, everyone in the west is a billionaire. Take for example eskimos. 99% of the time they eat meat. Just meat.Another misbelief is that expensive food is qualitatively better. Much of the so called organic farming food is full of bacteria and has lousy quality tests.

phi1: Rich people eat what their appetite tells them to eat. Many business people eat at fastfood restaurants all the time when on business tours.This is whining on a high level. Compared to poor contries, everyone in the west is a billionaire. Take for example eskimos. 99% of the time they eat meat. Just meat.Another misbelief is that expensive food is qualitatively better. Much of the so called organic farming food is full of bacteria and has lousy quality tests.

Yes, compared to poor countries, everyone in the west is a billionaire, which is one reason why most food is more expensive here.

Meat is expensive, compared to lentils and rice. But eating meat makes it easier to stay trim, because you're not overloading with carbs.

I don't think organic food is necessarily better. What I'm saying is that it's very cheap to eat mac and cheese everyday. Or pasta, or beans and rice. or crap off the dollar menu at BK/McDs. or lots of other things that are pretty tasty and give you the necessary calories, but also load you up with addictive foodstuffs that change your appetite in ways that make you fat.

Eating a lot more fresh vegetables and lean meats tends to change your appetite in ways that make you less fat. But it's *much* more expensive. Not so expensive that most people can't afford it, but expensive enough that people who are not at least middle class are making significant trade-offs when they choose to do it.

I speak from experience. I pay attention to this stuff. If I don't give a shit about my food health, I can eat about 40% cheaper than if I do.

Taste and variety are important enough to me that I'll go off a diet where they aren't on offer. And they just aren't available at a cheap price unless I'm eating foods that will mess up my appetite signals in ways that make me fat.

Note claims I'm not making. I didn't say squat about organic food. I never said that rich people aren't fat or all eat well or that it's easy for us to not get fat. Of course that's not true. Money isn't the only factor, there are lots of cultural factors also. But if you're well off the economic hit isn't that big, which IMO is probably why *somewhat fewer* rich people are fat than poor people.

If you doubt that it's difficult for the poor in our society to eat well, why don't you try living on a lower middle class food budget for a year? Not a month, anyone can do anything that doesn't kill them for a month. A year. Let's say you make 20k a year and live alone. A couple of reports I read from the consumer credit counseling people suggest that 15% is an average food budget. That's $250 a month. Feed yourself on $250 a month for a year and tell me that it's easy to eat a healthy diet that doesn't include addictive foods and ingredients and doesn't get old really fast.

A healthy diet is not that expensive. IMO the reason most people in the U.S. eat such a crappy diet is because they are used to convenience foods and don't know how to make a meal from ingredients. This used to be my case and probably would be still if I were not married.

Chicken is cheap. Eggs are cheap. Canned fish, including canned salmon, is cheap. Beans, lentils, etc are cheap. Yogurt is cheap (don't get the kind with corn syrup added). Olive oil is cheap. Frozen vegetables are cheap. Fresh apples, bananas, romaine lettuce by the head, and sometimes oranges are fairly cheap. Black pepper, onions, garlic, and salsa are all cheap.

Michael S suggested that a person could not eat well on $250/month. There are four of us in our family, we eat well and to our taste, and we spend less than $500/month on food. It is not hard, once you know how.

Humans have always richly valued natural fats, and eaten as much as they could. Not only that, but they selected hunting and eating patterns based around the desire to get even more fat. Yet, hunter-gatherer humans were in tremendous shape, taller, stronger, more robust than we post-agriculture humans are. So, fat consumption is definitely not the culprit.

The culprit is that tasty empty carbohydrates have become cheap enough for everyone to eat more than they need, while at the same time machines have replaced much of the physical labor we once did. A diet of potatoes and oatmeal tend to make a man fat, but if he's spending 65+ hours a week doing hard physical labor, it won't matter. Likewise, a paleo diet of meat and starchless vegetables will keep a man slim even though his hunting only takes 20 hours a week.

Today, we have the worst of both worlds. American poor eat a lousy diet of starches and sugars, and mostly don't perform hard physical labor. That leads to obesity pretty quickly.

Michael S suggested that a person could not eat well on $250/month. There are four of us in our family, we eat well and to our taste, and we spend less than $500/month on food. It is not hard, once you know how.

First of all, there are significant economies of scale. 500/mo for a family of four may be about equivalent in terms of budget difficulty to 250/mo for a single person. Does that also include all food, including going out to dinner?

Second -- I said it isn't easy, I didn't say it was impossible. I've done it. It is not hard in the sense that it requires knowledge or skill most people are incapable of learning. It is hard in the sense that it requires a fair bit of *work*, and extra time spent dealing with food.

My point is that there is a tradeoff, and if you have plenty of money to spend, it is *easier*, so it would be natural for people who have more money to be more successful.

At no time, have I ever suggested that it is *impossible* for poor (in american terms) people to eat well, or that it is trivial for rich people to eat well. Like most things in this world, it is marginally easier if you have more money. That means that people who have more money will probably do more of it than people who have less money -- other things being equal.

So my point is that as you get enough money that you are no longer struggling against malnourishment, it is still hard to eat *well* in ways that do not addict you to overeating -- so many people get fat. As you get even *more* money, it becomes easier to avoid food addiction, and fewer people get fat.

IOW. this difference explains the result that DF has seen.

I'm aware that libertarians are fond of assuming that poor people are just incompetent at everything, but some of their problems come from [SHOCK!] not having as much money.

We live in a community with a high hispanic population and have noticed that there are no skinny Mexicans, at least that we have ever seen. At best they are "normal" but curvy or stocky. Why is that? Diet? I eat Mexican food several times a week and weigh 110 (I'm 5' 5") Laziness? These people are very hard working. Genetics? Give me a break, I just can't beleive an entire race, covering a hugh geographical area, can all be affected by some kind of genetic problem.

What about all the ads in 1940s and 1950s US comic books selling products designed to rid girls of unwanted skinniness?

I read comics voraciously in the 50's, and I don't remember any such ads. Maybe you're thinking of the ones from Charles Atlas and Joe Weider which pitched muscle building/weight gain products to skinny boys. Those were in every issue.

Good thinking, but I think it's simpler than that. Poor people are probably fat for the same reason they're poor. Plenty of food (government provided, more often than not), not a lot to do but eat. In a lot of cases, it's pure laziness. In others, it's a lack of either the intelligence or imagination required to change bad habits. Either way, I don't think being poor in a developed nation causes obesity so much as it co-exists as an effect of other behavioral patterns.

Dr Friedman's argument isn't very convincing. The answer is simple and has been made in a number of earlier posts: individual financial success is typically the result of intelligence and self discipline. Intelligent, self-disciplined individuals are less likely to eat excessively.

You haven't really identified the motivation for the rich to get thin.

It is status. The rich will always attempt to distinguish themselves from the non-rich, by affecting whatever fashions work to this end. The ideal fashion is one that requires expenditures that the non-rich can't afford: typically, either in leisure time, or money, or both.

Thus, things like skiing, formerly associated with the wealthy and trendy because of that, have become middle class.

Fatness was formerly trendy, or at least trendier. (Men still insisted on certain female proportions. Women care less about men's appearance and many were just fat.) As soon as it became possible for the middle classes to become fat, it lost whatever glamor it had. When the poor followed the middle class into obesity, it has become positively anathema as the rich have pursued exercise and diet, and also plastic surgery, as means to once again distinguish themselves from the other classes.

"Like most processed foods, the Twinkie is basically a clever arrangement of carbohydrates and fats teased out of corn, soybeans and wheat — three of the five commodity crops that the farm bill supports, to the tune of some $25 billion a year.... For the last several decades — indeed, for about as long as the American waistline has been ballooning — U.S. agricultural policy has been designed in such a way as to promote the overproduction of these five commodities, especially corn and soy. That’s because the current farm bill helps commodity farmers by cutting them a check based on how many bushels they can grow, rather than, say, by supporting prices and limiting production, as farm bills once did. The result? A food system awash in added sugars (derived from corn) and added fats (derived mainly from soy), as well as dirt-cheap meat and milk (derived from both). By comparison, the farm bill does almost nothing to support farmers growing fresh produce. A result of these policy choices is on stark display in your supermarket, where the real price of fruits and vegetables between 1985 and 2000 increased by nearly 40 percent while the real price of soft drinks (a k a liquid corn) declined by 23 percent. The reason the least healthful calories in the supermarket are the cheapest is that those are the ones the farm bill encourages farmers to grow."

The wealthy have more choices on what to do with their time. Many choose to exercise. Few people who have exercised regularly all their life are obese.

Among poor people, take a look at those which have physically demanding jobs. Have you ever seen a farm laborer who is obese? Someone who eats unhealthily, say, two big macs a day, will usually still avoid obesity if he exercises daily.

Your conjecture is interesting, but I think there are larger effects to look at first.

I am not from USA, but i have been there few times. I tell, it was a shock to see for the first time people of this size. I do not mean to assult anyone. Seing the commercials on TV and seeing the food is being sold (every kind of diet, low sugar, less fat, natural, 1 ca...etc. It seemed it was all about big businesses: those that sell you the most "tasty food in the world", those that sell dieting drugs/ food supplements in "jars" of enormous size (coming from a previous soviet union country- this all was very funny and unusual)...and then at very end come the advertisments for sports equipments...How much drugs can you eat???(and a lot of these adds contained one and the same message: with this "wonder pill" you can eat as much as you want), so actually there is very little "propaganda" for healthy life styles.I agree that it seemes more a problem of the lower income parts of society. I guess "fast food" has lost its prestige for the richer people. I have not seen any place where McDonald's is open 24 hours a day..I mean do we really need burgers at 4 o'clock in the morning. So I agree it is about having the money to buy it, because food has become cheap but it is also about availability....if the McDonald's light is the only light shining in the darkenss of the night... So I say it is supply meeting demand, but there is a lot of "push strategy" here too.... I do not think we'd feel something is missing from our lives, if we did not know that there are say 20 possible types of burgers..probably more.I can see your point, that in Asia obesity can not be the direct result of exessive advertising, but I'd rather think that there it is in some way a sign of freedom and new culture - even though there are very traditional societies, I tend to think there this food is a sign of certain "new cool", certain life style... I saw a TV program once about chinese young people: cars and fast food - there it is rather a sign of cool life style, being able to afford it.

I believe the only thing that can stop it is more propaganda on healthy life styles, this has to be something that becomes "normal" to children from the early ages.. there for the food they receive at school should also be regulated.I wonder how much of it can be done... I guess the fast food lobby is not resting either.... they've enjoyed their rule for so long... they won't be giving it that easily.From what i have read about this problem... we can not avoid the psychological part part of it. There seem to some kind of addiction as well: to eat more and more, more than plenty. Ads if once on this track, they do not see the way out: cause gaining weight seems much easier than losing. So why do hard part?I really hope that our fast lifestyles, stress and so on..Yes our lifestyles have changed and this has also influenced thr growth of fast food. If I remeber correctly it all started with the fast growth of car users... and of course growth of income, food becoming cheaper and so on... I just hope that children born in the families of obese parents are not "forced" to follow their lifestyle: what we see most at certain moment is percieved as normal... So we must fight for it to become normal!

I take issue with your statement " I doubt the consumption patterns of people in India or China are much influenced by advertising." Not sure what this is based on (or the logic behind it).

Otherwise great arguments. One could actually observe (again, not scientifically) that the prototype of the nouveau riche in societies emerging from communism: that person was an obese male with nice car (no more walking anywhere), with a driver, and expensive clothes (and of course very attractive and young wife/lover). Now (10-15 years later), the same people are making publicized attempts at weight loss, and you can see many overweight people in the poorer segments of society (which would have stood out in the first 5-10 years after the end of communism). Again, these are my observations based on regular travel - but they do support your ideas.